Gas Exchange in Animals

159mm Hg

• Q = DA(P1 - P2)/L
• Q - the rate at which a substance diffuses between two location
• D - the diffusion coefficient, dependent on size and shape of diffusing substance, medium, and temperature
• A - the cross sectional area over which the substance is diffusing
• P1, P2 - the partial pressure of the gas at two locations
• L - is the disance between these locations

• Increase the surface area of exchange
• maximize the partial pressure gradient
• Proper ventilation of the respiratory medium
• Proper blood flow on the inside of the respiriatory suface
• Decrease distance between the two sides of the medium

• Easier to obtain O2 from air than water
• Air contains 20x more O2
• O2 diffuses 8,000 times more rapidyly
• Water breathers must work harder to breathe than air breathers

• As temperatures rise, so does the animal's metabolism and the need for more O2
• Warm water holds less O2 than cold water

• Because of the slow diffusion of O2 in water, the PPO2 of cells has to be 1-2mm Hg
• Animals w/o internal transport of O2 are either severly limited in size or have evolved bodies that are flattened or built around a central cavity

branched tubules in insects used for gas exchange

Gas exchange surface + the mechanisms used to ventilate and perfuse gas exchange surface

tracheae openings to the outside world

branches of the tracheae in insects where O2 is delviered to air capillaries very close to cell mitochondria

Bubble of air used by insects for breathing underwater

numerous cuticular hairs on the surface of an insect to maintain a constant gas gill

• Gills have high surface area
• Double pump system for ventilation (mouth and operculum)
• Constant one-way water flow over the gills maximizes PO2 on the external gill surface
• Counter-current blood flow maximizes O2 exchanged.

gas exchange surface for gills

break into gill filaments with lamella on the filaments

• Air flows unidirectionally through lungs to maximize gradients
• Air sacs connect to lungs to allow for unidirectional flow

further subdivizion of bronchi in birds that run parallel to one another

• One-way air flow but no air sacs
• Mechanism unknown
• Reminder: birds and crocodilians evolved from DINOSAURS RAWRRRR!

amount of air exchanged in a single breath at rest

maximum usable lung volume

• airways in which gas exchange cannot occur.
• Residual volume is the air that keeps the lungs from collapsing, part of the dead space

residual volume + vital capacity

• Enormous surface area
• Short path length for diffusion

A chemical substance that reduces the surface tension of a liquid

• Possible in premaure babies
• Alveoli don't produce surfactants yet

lift ribgs up or down to increase thoraic cavity